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動詞不定式的用法(2)
不定式也可以在作表語用的形容詞后面作狀語。如:I am very glad to hear it.
The question is difficult to answer.
“too + 形容詞或副詞 + 不定式”作狀語。如:
He is too old to do that.
另外,句子中有enough這個詞時,常用不定式作狀語。例如:
The room is big enough to hold us.
6)作表語。如:
My job is to help the patient.
7)作獨立成分。如:
To tell the truth, I don’t agree with you.
8)不定式與疑問詞who,which,when,where,how,what等連用,在句中起名詞作用,可充當主語、表語、賓語等。如:
He didn’t know what to say. (賓語)
How to solve the problem is very important. (主語)
注意:在與why連用時,只用于why或why not開頭的簡短疑問句中,后面緊跟的動詞不定式不帶to。例如:
Why not have a rest ?
9)不定式在句中用主動式還是被動式,多數情況下是容易判斷的,但有時的確比較復雜,請注意以下幾點:
①不定式修飾的名詞或代詞和不定式邏輯上構成主謂關系時,不定式往往用主動形式。如:
Have you got a key to unlock the door ?
(A key unlocks the door. )
、诓欢ㄊ胶退懊姹恍揎椀拿~或代詞構成邏輯上的動賓關系,又和該句主語構成邏輯上的主謂關系時,不定式常用主動形式。
I have got a letter to write. (I write letter. )
He needs a room to live in. (He lives in a room. )
I know what to do. (I do what. )
但這句如改為下列形式,不定式就得用被動形式:I know what is to be done.
這是因為what is to be done是賓語從句,從句中的主語what是動詞do的動作對象。
、鄄欢ㄊ阶鞅碚Z形容詞的狀語,和句中主語構成邏輯上的動賓關系時,不定式多用主動形式,這是因為人們往往認為形容詞后省去了for sb. 。如:
He is hard to talk to. (to talk to him)
The book is difficult to understand. (to understand the book)
、茉趖here be結構中,當說話人考慮的是必須有人去完成某件事時,不定式用主動形式;如果說話人強調的事情本身必須完成,則用被動形式。
There is a lot of work to do. (Somebody has to do the work. )
There is a lot of work to be done. (The work has to be done. )
請注意下面兩個句子的含義是不同的:
There is nothing to do. (無事可做,感到十分乏味。)
There is nothing to be done. (某東西壞了,無法使之恢復正常。)
2.不定式的時態(tài)
1)不定式的一般形式所表示的動作,通常與謂語的動作(狀態(tài))同時(或幾乎同時)發(fā)生,或是在它之后發(fā)生。例如:
I saw him go out.
2)如果謂語表示的動作(情況)發(fā)生時,不定式表示的動作正在進行,這時不定式就要用進行式。例如:
He pretended to be reading a book when she went in.
3)如果不定式的動作發(fā)生在謂語動詞之前,就要用完成式。例如:
I’m sorry to have kept you waiting.
3.不定式的語態(tài)
當不定式邏輯上的主語是這個不定式所表示的動作的承受者時,不定式一般要用被動形式。如:
He asked to be sent to work in the countryside.
It is possible for our hopes to be realized.
4.不定式符號to的保留問題
有時為了避免重復,可以用to來代替前面的不定式,這種情況常出現下列動詞后:expect,prefer,care,mean,forget,want,wish,hope,try以及be glad/happy等后。
如果在省略的不定式結構中含有be,have,have been,這些詞要保留。如:
—Are you on holidays ?
—No, but I’d like to be.
—I didn’t tell him the news.
—Oh, you ought to have.
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